With a certain type of conventional heat exchangers using a cylindrical pipe as a heat transfer pipe, the cylindrical pipe is formed in corrugated shape for improving the heat transfer characteristic (heat transfer efficiency). When such a heat exchanger is used in the food, bio-technological, and electronics industries and the like, it must meet the requirements that the intraductal liquid be able to be thoroughly discharged to the outside, and that the cleanability be improved and the level of sanitation be enhanced.
Especially, horizontal heat exchangers using a pipe formed in corrugated shape, however, have a drawback of that liquid accumulation is produced in the root of the corrugation, which makes it difficult to thoroughly discharge the residual liquid to the outside in draining or cleaning. Especially, for the processes for manufacturing pharmaceuticals, those in the electronics industry that use a cleaning liquid or pure water, the variety of processes in the bio-technological and food industries, and the like, the heat exchanger used must produce no residual liquid, thus, a satisfactory measure has been demanded.